The present invention relates to systems and methods for controlling the operation of automotive air conditioning compressors, especially variable displacement compressors which may be regulated for optimal operation for a particular engine operating state and environmental condition.
Electronically controlled automotive air conditioning compressors are well known in the prior art. Typically, prior art electronically controlled compressor systems include an electronic control module in communication with various sensors for measuring vehicle interior and exterior environmental conditions, switches for actuating various air conditioning system modes, output ports for relaying output signals to actuate various system components, such as vent doors, blower motor, fans, and valves.
These electronically controlled compressors require a control strategy to optimize system operation. Without a control strategy capable of optimizing the performance of the air conditioning system, there is little justification for electronically controlling the compressor as compared to mechanically controlling the compressor. Generally, electronically controlled compressor systems weigh more, are more expensive, and require more sensors than their mechanical counterpart.
However, with optimum control of the electronically controlled compressor systems, the inefficiencies of mechanically controlled compressors, that are operated at lower evaporator temperatures than otherwise required (typically around 35 F) may be avoided. Such air conditioning systems having mechanically controlled compressors, thus do more work than is required in the vast majority of operating conditions.
Therefore, what is needed is a new and improved method for controlling electronically controlled automotive air conditioning compressors. The new and improved method must not run the compressor unnecessarily. Moreover, it must not create a passenger compartment environment that is prone to fogging or is too humid.
A method for controlling a vehicle air-conditioning system for cooling an interior of a vehicle is provided. In an aspect of the present invention the vehicle air conditioning system has a compressor coupled to an electronic control valve. In another aspect of the present invention, the method includes reading a user manipulatable switch, determining a desired vehicle interior temperature based on the read user manipulatable switch, reading a plurality of sensors indicative of an interior and an exterior climate of the vehicle, determining a heat load on the vehicle air conditioning system, determining a desired evaporator discharge temperature, evaluating a humidity level inside the vehicle by determining a humidity ratio, filtering the updated electronic control valve duty cycle to obtain a new electronic control valve duty cycle based on the desired evaporator discharge temperature, and sending the new electronic control valve duty cycle to a compressor controller, wherein the controller is in communication with the electronic control valve and commands the valve to operate at the new duty cycle.